Agilent Technologies 856290216 service manual KHz Resolution Bandwidth Problems

*ATTEN 1 0 d B
R L 0dBm		lOdB/
	I		I	I

C E N T E R 300.0000MHz		S P A N 3.000MHz
*RBW 1.0MHz	VBW 1 .BMHz	SWP 50ms

S K 1 8 3

Figure 9-14. Faulty LC Pole

30 kHz Resolution Bandwidth Problems

Shape factor too high: Shape factor is the ratio of the 60 dB bandwidth to the 3 dB bandwidth. Shape factor should be less than 15:l. If one of the LC poles malfunctions, the shape factor may be the only indication of the failure. Isolate the non-functioning pole with the IF signature. Region E of Figure 9-8 illustrates the four LC-pole adjustments. Take several signatures to examine the LC-pole adjustments. If one of the four sections of Region E is consistently longer than the others, the corresponding LC pole is faulty.

IF gain compression: FET transistors Q301, Q303, Q700, and Q701 can deteriorate with age. Measuring less than 0 volts on the FET source indicates a bad FET.

Bandwidth too wide: Check for contamination on the printed-circuit board. Clean the board as required.

3 kHz and 10 kHz Resolution Bandwidth Problems

Asymmetric Filter Response: Check the crystal symmetry control with the following steps:

1.Press (KZZiJ

2.Set the HP 85623 spectrum analyzer controls as follows:

Resolution bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 kHz Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100kHz Center frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300 MHz

3.On the HP 85623 spectrum analyzer, connect the 300 MHz CAL OUTPUT to the INPUT 5os1.

4.A trace similar to Figure 9-15 indicates a failed crystal-symmetry circuit.

9-30 IF Section